Failed to launch debug
Hello,
STLink utility should be closed or at least not connected to the STLink of course.
On your custom board, did you connect the Reset line output from STlink to the STM32 reset input on your board ?
It is necessary to connect the Reset if you want to reconnect on an application already programmed that might use low power modes or SWD lines as io and SW4STM32 is using the Reset to connect to the target.
Rgds,
Laurent